Quote:
Originally Posted by Wishblade
I know its been said that LED lighting is supposed to reduce the amount of light reflecting back into the sky, but from what I've seen so far from them they actually make light pollution much worse. Halifax started switching several years back and the difference now is quite noticeable. As unfortunate as this is, I think the energy efficiency of them trumps this.
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It has more to do with the colour temperature of the light. High Pressure Sodium is between 1800-2200K, LED used for outdoor loghting is typically 4000K, sometimes 5000K. White light appears brighter to the human eye, so spillage may seem more aignificant even though it's either the same or less. LED fixtures used for roadway are directional, purely downlight, most HPS streetlights have at least 20% of the light going up.
A big problem with LED currently used outdoor is that it has a huge spike in the blue spectrum, which is what our bodies associate with daylight. This can cause major sleep disturbances. There is now a movement underway to persuade municipalities to use amber colour LEDs (ie. same as HPS) in order to prevent circadian rhythm disruption, however this hasn't really taken off in the market yet.
Major issue with amber LEDs is that it requires a thicker phosphor coating which decreases the efficiency by ~20% making for a slower ROI.
Source: I've been working in the lighting industry for the past 5 years